In foundries, devices such as bottom pour ladles, casting boxes and the like are used extensively to pour molten metal into moulds; these devices, which will hereinafter be referred to simply as ladles, are provided with a refractory nozzle in their bottom.
The flow of molten metal through the nozzle is known to be controlled in a number of ways. For example, it is known to have a refractory stopper in the interior of the ladle, the stopper being moveable with respect to the nozzle controlling the flow of metal. However, such a system has the problem, particularly in large ladles, that the stopper is long and cumbersome to adequately and accurately control.
An alternative system known in the art comprises a so called “slide gate”. A slide gate compromises a unit that is added beneath the nozzle having two plates which each have an aperture therethrough and are arranged to slide over each other to control the flow of molten metal. However, this system has the problem that when the gate is closed and the flow of metal stopped, the metal between the nozzle and the slide gate almost instantaneously freezes, thus blocking the outlet. In order to unblock the outlet, the gate has to be lanced to melt the frozen metal and restart the pouring process. This is a dangerous, time consuming and expensive process.
Thus a need exists in the art to provide a means of controlling the flow of molten metal from a ladle that allows the flow to be interrupted and restarted without freezing and which avoids the cumbersome, difficult to control, refractory stopper.